Methods for producing sucralose intermediates and sucralose from a feed stream comprising a sucrose-6-acylate in a reaction vehicle are known. For example, EP 0409549 discloses a process for the chlorination of a sucrose-6-acylate in a tertiary amide reaction vehicle to produce a sucralose-6-acylate, such as sucralose-6-acetate. A large excess of an acid chloride, such as phosgene, is used as the chlorination agent in this process. Following the chlorination reaction, the excess chlorinating agent is quenched using a suitable base, thereby forming the chloride salt of the base. The resulting product stream thus comprises a sucralose-6-acylate, the tertiary amide reaction vehicle, water, and salts.
A known method for obtaining sucralose from a product stream comprising a sucralose-6-acylate, a tertiary amide reaction vehicle, water, and salts, without isolation of the sucralose-6-acylate intermediate, is disclosed in EP 0708110. The process comprises deacylation of the sucralose-6-acylate before or after removal of the tertiary amide reaction vehicle, and then isolation of the sucralose. The removal of the tertiary amide (which is usually dimethylformamide [DMF]) is carried out by steam stripping.
According to EP 0708110, it is preferred to perform the deacylation after the removal of the reaction vehicle, because otherwise, during the deacylation step, base-catalysed decomposition of the reaction vehicle, in this case a tertiary amide, occurs. This hinders the subsequent isolation of the sucralose, and also means that the tertiary amide cannot be efficiently recovered and recycled. Thus, the tertiary amide reaction vehicle is removed from an aqueous solution of sucralose-6-acylate, and deacylation of the sucralose-6-acylate is carried out thereafter.
A process for the recovery of the tertiary amide prior to deacylation is disclosed in U.S. Pat. No. 5,530,106. This process involves steam stripping.
The steam stripping according to these prior art methods is very energy intensive.
The disadvantages of the known steam stripping process for removal of the reaction vehicle are discussed in WO 2005/090376 and WO 2005/090374. These references propose removal of all liquids after quench of the chlorination reaction to provide a solid residue, and to then obtain sucralose from the solid residue. According to this prior art, the removal of the liquids preferably takes place using an agitated thin film dryer.